Implantable lead with isolated contact coupling

ABSTRACT

An implantable lead for a medical device with an isolated contact connection for connecting a conductor to a contact reduces the opportunity for conductor material to migrate to a contact or into a patient. The implantable lead comprises a lead body having a proximal end and a distal end, at least one conductor, at least one contact carried on the proximal end, at least one contact carried on the distal end, at least one coupling. The lead has an exterior surface. The conductor is contained in the lead body and extends from the lead proximal end to the distal end. The conductor is electrically insulated. The contact carried on the proximal end is electrically connected to the conductor. The coupling has a conductor coupling and a contact coupling. The conductor coupling is placed over the conductor and attached to the conductor. The contact coupling exits the lead body and has a weld to connect the contact coupling to the contact. There is an isolation space created between the conductor and the contact to prevent the weld from containing conductor material.

CROSS REFERENCES

This application is a continuation in part of U.S. application Ser. No.10/128,883, filed, Apr. 22, 2002, now U.S. Pat. No. 7,184,840, issued onFeb. 27, 2007.

BACKGROUND OF THE INVENTION

This disclosure relates to medical devices and more particularly to animplantable lead.

The medical device industry provides a wide variety of electronic andmechanical devices for treating patient medical conditions such aspacemaker, defibrillators, neuro-stimulators, and therapeutic substancedelivery pumps. Medical devices may be configured to be surgicallyimplanted or connected externally to the patient receiving treatment.Clinicians use medical devices alone or in combination with therapeuticsubstance therapies and surgery to treat patient medical conditions. Forsome medical conditions, medical devices provide the best and sometimesthe only therapy to restore an individual to a more healthful conditionand a fuller life. One type of medical device is an implantableneurological stimulation system that can be used to treat conditionssuch as pain, movement disorders, pelvic floor disorders, gastroparesis,and a wide variety of other medical conditions. The neurostimulationsystem typically includes a neurostimulator, a stimulation lead, and anextension such as shown in Medtronic, Inc. brochure “ImplantableNeurostimulation System” (1998). More specifically, the neurostimulatorsystem can be an ITREL II® Model 7424 or an ITREL 3® Model 7425available from Medtronic, Inc. in Minneapolis, Minn. that can be used totreat conditions such as pain, movement disorders and pelvic floordisorders. The neurostimulator is typically connected to a stimulationlead that has one or more electrodes to deliver electrical stimulationto a specific location in the patient's body.

Implantable leads have conductors that are connected to contacts to formelectrical paths. The connection between the conductors and the contactsshould have a solid mechanical connection and a low impedance electricalconnection for efficient operation and reliability. Conductorsmanufactured from low impedance materials such as silver make forming aconnection with good mechanical properties challenging because silverhas substantially less tensile strength than a more common conductormaterial such as MP35N. Additionally, silver content in the weld jointbetween a conductor and contact increases the chances of separation,silver exposure to tissue, and weld corrosion during lead operation.Some previous connections directly connect the conductor to the contactbut sometimes the conductor material is not ideal for forming a strongmechanical connection. Additionally, conductor material such asconductor ions can migrate from the conductor to the contact or evenfrom the conductor into the patient. Other previous connections use atube crimped to the conductor that is welded to the contact. Althoughthe tube can improve the mechanical connection, material from theconductor can still migrate from the conductor to the contact or intothe patient. An example of a lead with a joined conductor and electrodeis shown in U.S. Pat. No. 6,181,971 “Joining Conductor Cables AndElectrodes On A Multi-Lumen Lead Body” by Doan (Jan. 30, 2001).

For the foregoing reasons, there is a need for an implantable lead withisolated contact couplings to reduce the opportunity for conductormaterial to migrate to the contact or into the patient.

BRIEF SUMMARY OF THE INVENTION

An implantable lead with an isolated contact connection for connecting aconductor to a contact reduces the opportunity for conductor material tomigrate to a contact or into a patient. The implantable lead comprises alead body having a proximal end and a distal end, at least oneconductor, at least one contact carried on the proximal end, at leastone contact carried on the distal end, at least one coupling. The leadhas an exterior surface. The conductor is contained in the lead body andextends from the lead proximal end to the distal end. The conductor iselectrically insulated. The contact carried on the proximal end iselectrically connected to the conductor, and the contact carried on thedistal end is also electrically connected to the conductor. The couplinghas a conductor coupling and a contact coupling. The conductor couplingis placed over the conductor and attached to the conductor. The contactcoupling exits the lead body and has a weld to connect the contactcoupling to the contact. There is an isolation space created between theconductor and the contact to prevent the weld from containing conductormaterial.

Another aspect of the present invention provides for an implantable leadwith a coplanar coupling for connecting a conductor to a contact toreduce conductor bending moments to improve lead reliability. Theimplantable lead comprises a lead body having a proximal end, a distalend, at least one conductor, at least one contact carried on theproximal end, at least one contact carried on the distal end, and atleast one coupling. The conductor is contained within the lead body andtraverses from the proximal end to the distal end of the lead body. Thecontact carried on the proximal end and the contact carried on thedistal end are electrically connected to the conductor. The conductorcoupling is partially placed over the conductor and attached to theconductor. The conductor coupling is then placed in a channel on the atleast one contact and welded to connect the conductor coupling to the atleast one contact. An isolation space is created between the conductorand the contact to prevent directly welding the conductor to thecontact.

Another aspect of the present invention provides for a method forperforming a coplanar connection between a conductor and a contact on animplantable lead to reduce conductor bending moments and improve leadreliability. A conductor is inserted into a crimp sleeve cavity and thencrimped to securely attach the conductor to the crimp sleeve. The crimpsleeve is then inserted into a channel located on the contact. The crimpsleeve is then welded to the contact wherein the crimp sleeve cavity islocated a sufficient distance away from the weld to substantiallyprevent the conductor from being damaged by the weld.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a general environmental view for a neurostimulation systemembodiment;

FIG. 2 shows a neurostimulation system embodiment;

FIG. 3 shows an implantable lead embodiment;

FIG. 4 shows an implantable lead with cross-section indicationembodiment;

FIG. 5 shows a cross section of the implantable lead embodiment shown inFIG. 4;

FIG. 6 shows an implantable lead with proximal end enlargementindication embodiment;

FIG. 7 shows an enlarged cross section of the proximal end shown in FIG.6;

FIG. 8 shows an implantable lead with distal end enlargement indicationembodiment;

FIG. 9 shows an enlarged cross section of the distal end shown in FIG. 8embodiment;

FIG. 10 shows a stylet with distal end enlargement indicationembodiment;

FIG. 11 shows the enlarged distal end shown in FIG. 10 embodiment;

FIG. 12 shows an implantable lead with enlargement indication of acontact embodiment;

FIG. 13 shows a cross section of the enlarged contact embodiment;

FIG. 14 shows an isometric view of a contact and coupling embodiment;

FIG. 15 shows an isometric view of the coupling embodiment shown in FIG.14;

FIG. 16 shows a flow chart of a method for creating an isolation spacein an implantable lead contact connection embodiment;

FIG. 17 shows a flow chart of a method for creating a coplanarconnection in an implantable lead between a conductor and a contactembodiment;

FIG. 18 shows an isometric view of a contact and coupling embodiment;

FIG. 19 shows a connection embodiment between a conductor and acoupling;

FIG. 20 shows an elevated top view of the contact and couplingembodiment of FIG. 18;

FIG. 21 shows a front profile view of the contact and couplingembodiment of FIG. 18;

FIG. 22 shows a front profile view of a coupling embodiment;

FIG. 23 shows a section of an implantable lead with contacts;

FIG. 24 shows an implantable lead with an end contact removed;

FIG. 25 shows another contact embodiment;

FIG. 26 shows another contact embodiment;

FIG. 27 shows another contact embodiment; and

FIG. 28 shows another contact embodiment;

FIG. 29 shows another contact embodiment.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 1 shows a general environmental view of an implantableneurostimulation system embodiment and FIG. 2 shows a neurostimulationsystem embodiment. Neurostimulation systems are used to treat conditionssuch as pain, movement disorders, pelvic floor disorders, gastroparesis,and a wide variety of other medical conditions. The neurostimulationsystem 20 includes a neurostimulator 22 such as an ITREL II® Model 7424or an ITREL 3® Model 7425 available from Medtronic, Inc. in Minneapolis,Minn., a stimulation lead extension 24, and a stimulation lead 30. Theneurostimulator 22 is typically implanted subcutaneously in thepatient's body 18 at a location selected by the clinician. Thestimulation lead 30 is typically fixed in a place near the locationselected by the clinician using a device such as the adjustable anchor.The implantable lead 30 can be configured as neurological stimulationlead, a neurological sensing lead, and a combination of both as aneurological stimulation and sensing lead, a cardiac lead and the like.

FIG. 3 shows an implantable lead embodiment. An implantable leadcomprises a lead body 32, at least one conductor 34, at least twocontacts 36. The lead body has a proximal end 38, a distal end 40, andan exterior surface 44. The lead body 32 can be composed of a widevariety of electrically isolative materials and configurations.Materials may include, but are not limited to, silicone rubber,polyurethane, fluoropolymers and the like. Configurations could includemonolumen and multilumen lead bodies. The exterior surface 44 iscomposed of one or more biocompatible materials.

The conductor 34 is contained in the lead body and generally extendsfrom the lead proximal end 38 to the distal end 40. The conductors 34can be manufactured from a wide range of materials that are electricallyconductive such as MP35N, platinum and the like. In some embodiments,the conductor 34 can comprise a plurality of wires that can beconfigured as braided strand wire (BSW). BSW is available in manyconfigurations including seven wire BSW. When low impedance is desired,the core of each wire can be manufactured from a low impedance metalsuch as silver and the jacket can be manufactured from a material withgood mechanical strength properties such as MP35N. One embodiment ofconductor 34 uses seven wire BSW with a silver core and an MP35N jackettypically with a resistance of less than about 0.098 ohms/cm (3ohms/foot) and a tensile strength greater than 5N. The conductor 34 canbe electrically insulated with a flouro-polymer such asethyletetraflouroethylene with a coating thickness of approximately0.0002 cm (0.0008 inch).

The contacts 36 includes at least one contact 36 carried on the leaddistal end 40 that is electrically connected to the conductor 34 and atleast one contact 36 carried on the proximal end 38 that is electricallyconnected to the conductor 34. The proximal contacts are typicallymanufactured from a material with good mechanical strength andbiocompatible properties such as MP35N and the like to withstandinteraction with mating devices such as an implantable neurologicalextension. The distal contacts are typically manufactured from materialswith good electrical and biocompatibility properties such as platinumand iridium alloys that can be configured in a mixture such as 90%platinum and 10% iridium. In some embodiments, spacers 46 are insertedbetween contacts 36 so the proximal end 38 and distal end 40 aresubstantially iso-diametric.

FIG. 4 shows an implantable lead embodiment, and FIG. 5 shows a crosssection of the implantable lead in FIG. 4. An implantable lead withimproved conductor lumens comprises a lead body 32, a stylet lumen 100,at least one conductor lumen 102, and at least one axial slit 42. Thelead body has an internal portion 104 and an external portion 106. Thestylet lumen 100 and the conductor lumen 102 are formed in the internalportion 104. The internal portion 104 is a continuous material that hasa proximal end 38, distal end 40, and an outer surface that isencapsulated by the external portion 104. This structure can be extrudedand its configuration can be substantially the same at any longitudinalcross section. The internal portion 104 has an outside diameter smallerthan the inside diameter of the external portion 106. In someembodiments, the internal portion 104 outside diameter is approximately0.102 cm (0.04 inch) smaller than the external portion 104 insidediameter. The internal portion 104 is fitted inside of the externalportion 106. The external portion 106 exterior surface 44 typically hasan outer diameter selected for the therapeutic application such as inthe range from about 0.05 cm (0.02 inch) to about 0.20 cm (0.08 inch)with one embodiment having an outer diameter of about 0.127 cm (0.05inch). The stylet lumen 100 is formed in the internal portion 104typically in the center and sized to provide clearance between thestylet lumen 100 and the coaxially inserted stylet wire 404 in the rangefrom about 0.00025 cm (0.0001 inch) to about 0.025 cm (0.01 inch), andin some embodiments that clearance is about 0.0038 cm (0.0015 inches).

The conductor lumen 102 is formed in the internal portion 104 andpositioned near an outer surface of the internal portion 104 such thatthere is only a web 110 between the conductor lumen 102 and the outersurface of the internal portion 104. Some embodiments have a pluralityof conductor lumens 102 such as in the range from about two to sixteenconductor lumens 102. The implantable lead embodiment shown has fourconductor assembly lumens that are substantially equidistant from eachother and to the centrally localized stylet lumen. The conductor lumens102 and stylet lumen 100 geometry provides axial stability, and thecentrally located stylet lumen 100 improves navigation. Each conductorlumen 102 can be configured to resemble a polygon that is notnecessarily symmetrical, and each conductor lumen 102 has a diametertypically greater than about 0.0254 cm (0.01 inch). In some embodiments,the conductor lumens 102 electrically insulate each conductor 34 andphysically separate each conductors 34 to facilitate identification ofthe conductor 34 that is appropriate for its single correspondingcontact 36. The film 108 thickness between the conductor lumens 102 andthe stylet lumen 100 is no less than about 0.00254 cm (0.001 inch). Thisfilm 108 is flexible enough to allow the entering stylet to slidethrough the lead body without penetrating through into a conductor lumen102 or out of the lead body.

The web 110 allows an axial slit 42 to be created in the internalportion 104 distal end for a path to exist between the conductor lumen102 and the internal portion 104 outer surface. The web 110 is nogreater than 0.005 cm (0.002 inch) thick. The web 110 provides the meansfor a conductor lumen 102 formed inside the lead body to be positionednear the exterior surface 44 of the lead body. The axial slit 42 isformed in the internal portion 104 distal end between the conductorlumen 102 and the outer surface of the internal portion 104. The axialslit 42 provides a temporary opening for a coupling 112 (FIG. 9) to exitthe conductor lumen 102 and attach to a contact 36. The axial slit 42,when stretched ajar, opens to a width of at least about 0.01 cm (0.0039inch) to allow the coupling 112 to exit the conductor lumen 102. Oncethe coupling 112 is connected to the contact 36, the axial slit 42preferably seals back.

FIG. 6 shows an implantable lead with proximal end 38 enlargementindication embodiment, and FIG. 7 shows an enlarged cross section of theproximal end 38 shown in FIG. 6. An implantable lead with improvedstylet lumen comprises a lead body, at least two conductors 34, contacts36, and a proximal flare 200. The lead body has a proximal end 38, adistal end 40, a stylet lumen 100, and at least two conductor lumens102. The conductors 34 are contained in the conductor lumens 102extending from the lead proximal end 38 to the distal end 40. Thecontacts 36 are carried on the distal end 40 and electrically connectedto the conductors 34. Typically, conductors 34 are also carried on theproximal end 38 and electrically connected to the conductors 34.

The proximal flare 200 is formed on the lead body proximal end 38 and ithas tapering walls that narrow toward a stylet opening to guideinsertion of a stylet (FIG. 10) into the stylet lumen 100, and theproximal flare 200 seals the conductor lumens 102 proximal end toisolate the conductor lumens 102. The proximal flare 200 is manufacturedfor a non-rigid material typically similar to the lead body material.The tapering walls have a slope typically in the range from about 0.25cm/cm to about 0.50 cm/cm. The axial length of the flare 200 is nogreater than about 0.064 cm (0.025 inches). The wall thickness of theflare 200 ranges from 0.01 cm (0.004 inch), at the most proximal end, to0.05 cm (0.019 inch), at the distal end of the flare 200. The proximalflare 200 is flexible to reduce stylet deformation during insertion orwithdrawal of the stylet. During stylet insertion into the stylet lumen100, navigation, and withdraw, the tapered walls absorb energy andstretch to accommodate movement of the stylet to reduce styletdeformation. Also during stylet insertion into the stylet lumen 100, theproximal flare 200 substantially prevents the stylet from entering theconductor lumens 102. The flare 200 provides a progressive tactilefeedback to indicate to the clinician the amount of stylet pressurebeing applying to the lead proximal end 38, which reduces lead/styletdamage or deformation during implant.

The proximal flare 200 seals the conductor lumens 102 proximal end toisolate the conductor lumens 102. The forming of the flare 200 placesmaterial in the conductor lumens 102 that typically extends no fartherthan the beginning of the conductors 34 located within the conductorlumens 102. Sealing the conductor lumens 102 minimize electricalconductance between the conductors 34, fluid migration into the lumensor other attached neurological devices, and unwanted stylet introductioninto the conductor lumens 102. The proximal flare 200 is manufacturedfrom a non-rigid material that can be the same material as the leadbody. The flare 200 can be formed by inserting the proximal end 38 ofthe lead body into a mold that has a conical shape. This conical shapeis inserted axially into the center stylet lumen 100. Heat istransferred from the conical mold to the polyurethane internal portion104 that seals the outer lumens and creates the flare 200.

FIG. 8 shows an implantable lead with distal end 40 enlargementindication embodiment, and FIG. 9 shows an enlarged cross section of thedistal end 40 shown in FIG. 8. An implantable lead with an improveddistal tip 300 comprises a lead body, at least two conductors 34,contacts 36, a stylet lumen 100, conductor lumens 102, and a distal tip300. The lead body has a proximal end 38, a distal end 40, a styletlumen 100, and at least two conductor lumens 102. The at least twoconductors 34 contained in the conductor lumens 102 extending from thelead proximal end 38 to the distal end 40. The at least two contacts 36carried on the proximal end 38 are electrically connected to theconductors 34. The at least two contacts 36 carried on the lead distalend 40 are also electrically connected to the conductors 34.

The formed distal tip 300 seals the conductor lumens 102 free fromadhesive or solvents. The conductor lumens 102 closed off by the formeddistal tip 300 improve electrical isolation between the conductors 34.The formed distal tip 300 penetrates the lumens 100, 102 of the leadbody. The material filling reaches no further into the lumens thanmaking contact to the enclosed conductors 34.

The distal tip 300 can be formed from the lead body by inserting into amold; this mold has the shape of the desired distal tip 300. The distaltip 300 has a diameter approximately equal to the lead final diameter ofapproximately 0.127 cm (0.05 inch). The heat conducted from the mold tothe lead distal tip 300, melts the surrounding material into theconductor lumen 102 and into the stylet lumen 100, completely sealingthem from the outside. Sufficient material is left between the lumens100, 102 to the outside of the lead such that substantial force would beneeded to perforate, if at all, through the finally formed distal tip300. The formed distal tip 300 is of the same material of the lead bodyand significantly minimizes the possibility of separation from the leadbody.

The distal tip 300 is substantially symmetrical since there is no needto align a separate distal tip 300. The distal tip 300 is symmetricallyformed such that it is coaxial with the lead body. Symmetry is desirablefor minimized protuberances from the exterior lead surface 44, thusreducing the potential of lead body ruptures. The symmetrical formationof the distal tip 300 also reduces physical and material discontinuitiesin the distal tip 300 to improve the navigational sensitivity of thelead 30 during implant potentially reducing operating room time.

The distal tip 300 is a more robust stylet stop which reduces theopportunity for stylet penetration of the lead body distal end 40. Thematerial penetrates the most distal end of the stylet lumen 100 by about0.15 cm (0.059 inch) into the stylet lumen 100 of the lead beginningfrom the most distal end of the hemi-spherical distal tip 300. The forcetransfer required for perforation of the lead distal end 40 issignificantly increased, therefore, reducing any potential of tissuedamage due to an exiting stylet and reducing the potential of creatingan opening in the lead which may disable electrical properties of thedevice.

FIG. 10 shows a stylet with stylet distal end 400 enlargement indicationembodiment, and FIG. 11 shows the enlarged distal end shown in FIG. 10.An implantable lead with an improved stylet comprises a lead body, astylet lumen 100, at least one conductor 34, contacts 36, and a stylet.The lead body has a proximal end 38, a distal end 40, an exteriorsurface 44, and a stylet lumen 100 contained inside the lead body. Theconductor 34 is contained in the lead body and generally extends fromthe lead proximal end 38 to the distal end 40. The conductor 34 iselectrically insulated by the lead body. There is at least one contact36 carried on the lead proximal end 38 that is electrically connected tothe conductor 34, and there is at least one contact 36 carried on thelead distal end 40 that is electrically connected to the conductor 34.

The stylet is composed of a stylet handle 402 that attaches to theproximal end 38 of the lead and a stylet wire 404. The stylet wire 404is configured for insertion into the stylet lumen 100 with a straightportion 406, a curved portion 408, and a ball tip 410 on the styletdistal end 400. The straight portion of the lead has a diameter of about0.0254 cm (0.01 inch) and has a parylene insulation of about 1.0 micron.The electrical insulation also serves as a coating that has a lowercoefficient of friction than the stainless steel of the stylet wire 404.

The curved portion of the stylet wire 404 has an angle, between thetangent of the curved portion and the straight portion that increases asthe curve approaches the stylet distal end 400. The curved portionbegins at about less than 3.75 cm (1.48 inches) from the stylet distalend 400 of the stylet wire 404. The most distal angle of the curvedportion has an angle greater than about 15 degrees from the straightportion.

The tangent of the curve with respect to the straight portion of styletincreases linearly as the curve approaches the stylet distal end 400.Once fully inserted into the lead, the stylet/lead results in a distalend angle that allows the physician to manipulate the device into thedesired location over the epidural space. The continuous and incrementalcurve of the lead distal tip 300 aids the physician to guide the leadpast anatomical obstructions, that would otherwise, hinder the ease ofintroduction of the lead to its designated location for stimulation.

The ball tip 410 is spherical and has a diameter that is greater thanthe stylet diameter and is no greater than the stylet lumen 100 innerdiameter. The ball tip 410 is configured to ease insertion of the styletwire 404 through the stylet lumen 100 to the stylet distal end 400. Theball tip 410 functions by stretching the lumen where the stylet wire 404is inserted to ease insertion of the remaining portion of the styletwire 404. In addition, the ball tip 410 reduces abrasion to the styletlumen 100 to reduce the risk of the stylet wire 404 protruding into theadjacent conductor lumens 102 or out of the exterior surface 44 of thelead body.

FIG. 12 shows an implantable lead with contact 36 enlargementindication, and FIG. 13 shows a cross section of an enlarged contact 36embodiment. The coupling 112 has a conductor coupling 500 and a contactcoupling 502. The conductor coupling 500 and the contact coupling 502are manufactured from a material with good mechanical and electricalproperties such as MP35N and the like. The conductor coupling 500 isplaced over the conductor 34 and attached to the conductor 34mechanically. The contact coupling 502 exits the lead body and has aweld 504 to connect the contact coupling 502 to the contact 36. The weld504, such as a laser weld, can be performed substantially on the contact36 exterior surface 44 for ease of manufacturing. The weld 504 isperformed such that the weld 504 pool is typically contained within thecontact 36 perimeter. In addition, the weld 504 height is controlled tobe less than about 0.0127 cm (0.005 inch), so interaction with otherdevices is facilitated. Each contact 36 has a contact slot 508 openingthat in some embodiment is in the range from about 0.0127 cm (0.005inch) to about 0.0381 cm (0.015 inch) in width and at least about 0.0508cm (0.020 inch) in length. In other embodiments, the contact slot 508can extend the entire length of the contact 36.

An isolation space 506 is created between the conductor 34 and thecontact 36 to prevent directly welding the conductor 34 to the contact36. The isolation space 506 separates the conductor 34 from the weld 504to substantially prevent the conductor 34 from contacting the weld 504.The isolation space 506 is necessary since silver is not wanted in theweld 504 pool because silver potentially weakens the strength andintegrity of a weld 504. In addition, it is desirable to avoid havingsilver contact the outside surface of the lead to avoid any directcontact with tissue. Although silver contact with tissue is notconsidered harmful, the separation serves as an additional precaution.The isolation space 506 is greater than about 0.05 cm (0.02 inch). Theisolation space 506 serves as a means for isolation created between theconductor 34 and the contact 36 to prevent directly welding theconductor 34 to the contact 36. In some embodiments, the isolation spacecan include a fill material such as epoxy.

FIG. 14 shows an isometric view of a contact 36 and coupling 112embodiment, and FIG. 15 shows an isometric view of the coupling 112embodiments shown in FIG. 14. In this embodiment, the isolation space506 is provided by the specific geometry of the contact coupling 502 andmore specifically the non-welded material between the conductor 34 andthe weld 504 to the contact 36. The non-welded material is sizedappropriately for the dimensions of the lead such as greater than about0.005 cm (0.002 inches). In this embodiment, the interface between theouter surface of the contact 36 and the other surface of the coupling500 can be continuously welded along selected sides of the interface orintermittently welded along the interface.

FIG. 16 shows a flow chart of a method for creating an isolation space506 in an implantable lead contact connection embodiment. The method forcreating an isolation space 506 comprises the following elements. Acoupling 112 is attached 510 to a conductor 34 so that the conductor 34extends into a first coupling region 500 of the coupling 112. Thecoupling 112 has a second coupling region 506 that is adjacent to thefirst coupling region 500 and a third coupling region 502 adjacent tothe second coupling region 506. An isolation space 506 is created 520and formed by the second coupling region 506. The isolation space 506 isvoid of the conductor 34. The third coupling region 502 is engaged 530into a contact slot 508 formed in a contact 36. The third couplingregion 502 is welded 540 to the contact 36 creating a contact weld 504.

In the coupling 112 embodiment shown in FIG. 13, the method for creatingan isolation space 506 in an implantable lead contact connection isperformed as follows. A coupling 112 is attached to a conductor 34distal end so that a first coupling region 500, a second coupling region506, and a third coupling region 502 are formed. The first couplingregion 500 is mechanically attached to the conductor 34 in a crimpingprocess that substantially reduces the diameter of the first couplingregion 500 such that it engages the conductor 34 firmly. Duringmechanical attachment, the crimping force is adjusted to obtain anadequate pull strength while avoiding undesired damage/deformation tothe wire 404. The conductor 34 distal end extends into the firstcoupling region 500 of the coupling 112. The second coupling region 506is distal to the first coupling region 500, and the third couplingregion 502 is distal to the second coupling region 506. The first regioncan be about 0.10 cm (0.04 inch) long, the second region can be about0.05 cm (0.02 inch) and the third region can be about 0.076 cm (0.03inch) long. An isolation space 506 is created and formed by the secondcoupling region 506, with the isolation space 506 void of the conductor34. The isolation space 506 is void of the conductor 34 so that the weld504 encompasses the third region and the contact 36.

The assembly consisting of the conductor 34 and the attached couplings112 on either end can be fed through a lead body. The placement of theassembly is such that the proximal coupling is on the proximal end 38 ofthe lead body and the distal coupling is on the distal end of the leadbody. The contact 36 with a contact slot 508 is placed on the lead bodydistal end. The contact slot 508 width is slightly less than thediameter of the third coupling region 502. The length of the contactslot 508 is greater than the diameter of the coupling 112 to allow forplacement anywhere along its length. The contact slot 508 assists inholding the coupling 112 in place prior to welding the third region tothe contact 36.

An axial slit 42 is created in the lead body distal end. The axial slit42 is long enough such that it allows for an opening of at least thediameter of the third coupling region 502. The coupling 112 attached tothe conductor 34 is exited through the axial slit 42 in the lead bodydistal end. The axial slit 42 permits the coupling 112 to pass throughto mate to the contact 36 with the minimum amount of movement of theconductor 34 assembly within the lead body. Also, the axial slit 42allows for a minimum sized path to exist between the conductor lumen 102and the contact 36. In the creation of the axial slit 42, material isnot removed, only a cut is made such that it allows the passage of thecoupling 112 from the conductor lumen 102 to the contact slot 508 area.The cut is created with a sharp razor and extends for about 0.076 cm(0.030 inch). It is made approximately under the location where thecontact 36 will be placed over and mate with the coupling 112.

The third coupling region 502 is bent in the range from about 85 degreesto about 120 degrees in relation to the longitudinal axis of theconductor 34. The bend can be made with a tool the size of a wrench thatcreates a bend beginning at the same location of the coupling 112,roughly 0.076 cm (0.03 inch) distally. The third coupling region 502distal end is formed into a contact coupling 502 that is complimentaryto a contact slot 508. The diameter of the third coupling region 502 isdeformed such that it closes the conductor 34 void opening of the thirdcoupling region 502. Also, the formed final geometry of the third regionof the coupling 502 has an interference fit with the contact slot 508.

The contact coupling 502 is engaged into the contact slot 508. Theentire perimeter and cross section of the third region 502 is placedwithin the open area of the contact slot 508. At this point the thirdcoupling region 502 is held by the contact slot 508 and is ready for amore secure attachment. The contact coupling 502 is welded to thecontact slot 508. The weld 504 can be created with a laser welder thatheats up the slot 508 region of the contact 36 and the third region ofthe coupling to the point where they become an alloy. The weld 504 bumpcreated is no greater than about 0.013 cm (0.005 inch) over the surfaceof the contact 36. Also, the weld 504 bridges over each end of the slot508 to provide mechanical integrity. The inner void of the thirdcoupling region 502 distal end is sealed by the weld 504. The weld 504surface area extends over the third region 502 of the coupling and theproximate perimeter of the contact slot 508. The weld 504 materialcreates a closed section in the third region 502 opening creating aclosed section of the coupling distal end (third coupling region 502).

FIG. 12 shows an implantable lead with contact enlargement indication,and FIG. 13 shows a cross section of an enlarged contact embodiment. Animplantable lead with coplanar contact connection comprises a lead bodyhaving a proximal end 38 and a distal end 40, at least one conductor 34,at least one contact 36 carried on the proximal end 38, at least onecontact 36 carried on the distal end 40, and at least one coupling 112.The lead body 32 has an exterior surface 44. The conductor 34 iscontained in the lead body 32 and extends generally from the leadproximal end 38 to the distal end 40. The conductor 34 is electricallyinsulated. There is at least one contact 36 carried on the proximal end38 that is electrically connected to the conductor 34, and at least onecontact 36 carried on the distal end 40 that is electrically connectedto the conductor 34. The coupling 112 has a conductor coupling 500 and acontact coupling 502. The conductor coupling 500 is placed over theconductor 34 and attached to the conductor 34. The contact coupling 502exits the lead body and is welded to connect the contact coupling 502 tothe contact 36 carried on the distal end 40. The contact coupling 502 isfurther configured to exit the conductor lumen 102 and mate with thecontact 36 while retaining the conductor 34 coplanar to the contact 36.The coplanar relationship between the conductor 34 and the contact 36 issuch that the longitudinal axis of the conductor 34 is maintainedsubstantially parallel to the longitudinal axis of the contact 36.

In some embodiments such as shown in FIG. 13, the contact coupling 502can be bent to exit the conductor lumen 102 and mate with the contact 36while maintaining the conductor 34 coplanar to the contact 36. Thecontact coupling 502 bend serves as a means for orienting the contactcoupling 502 to exit the conductor lumen 102 and mate with the contact36. The contact coupling 502 can be bent in the range from about 85degrees to about 120 degrees in relation to the conductor 34. In otherembodiments such as shown in FIGS. 14 and 15, the geometry of thecontact coupling 502 is such that the contact coupling 502 does notrequire mechanical deformation of the second region 506 or third region502.

The conductors 34 are contained within the lumens throughout the leadbody, such that it does not exit the lead at any point. The conductor 34is parallel to the lead body in its entire length. This allows theconductor 34 to not directly contact the outside surface of the lead orthe surrounding tissue. Conductor 34 stresses are significantly reducedby not allowing the conductor 34 to have a bending moment. Leadreliability is improved as a result from this coplanar conductor 34 tocontact 36 attachment.

FIG. 17 shows a flow chart of a method for creating a coplanarconnection in an implantable lead between a conductor 34 and a contact36 embodiment., The method for creating a coplanar connection in animplantable lead between a conductor 34 and a contact 36 comprises thefollowing elements. A coupling 112 is attached 600 to a conductor 34distal end, so the conductor 34 distal end extends into a first couplingregion 500 of the coupling. The coupling 112 has a second couplingregion 506 adjacent to the first coupling region 500. The couplingsecond region 506 is positioned 610 in a conductor lumen 102 adjacent620 to a contact 36. The second region 506 is welded 62 to the contact36 creating a contact weld 504. The conductor 34 distal end ismaintained in a coplanar relation 630 to the contact 36.

FIG. 18 shows an isometric view of another contact 36 and coupling 112embodiment providing an isolation space 506 between conductor 34 andcontact 36. This embodiment is comprised of contact 36, coupling 112,conductor coupling 500, contact coupling 502, isolation space 506,contact slot 508, and counter-boar 640. Contact 36 and coupling 112 aremanufactured from a material with good mechanical and electricalproperties. In a preferred embodiment all contacts 36 and couplings 112carried on distal end 40 are comprised of a platinum-iridium alloy. Morespecifically it is preferred that all contacts 36 and couplings 112carried on the distal end are comprised of a platinum-iridium alloy thatis 90% platinum and 10% iridium. The platinum-iridium alloy provides ahighly conductive and corrosion resistant electrical contact. Further,in a preferred embodiment all contacts 36 and couplings 112 carried onthe proximal end are comprised of MP35N to provide reliable contact whenproximal end 38 is inserted into a neurostimulation system extension orneurostimulator. MP35N is used for the proximal end contacts 36 andcouplings 112 because of its corrosion resistance and favorablemechanical properties which makes contacts 36 and couplings 112 moreresistive to damage when the implantable lead is utilized withneurostimulation systems which utilize set screws to hold theimplantable lead within the stimulation lead extension orneurostimulator. However, it is filly contemplated that contacts 36 andcouplings 112 carried on proximal end 38 and 40 can be of any type ofelectrically conductive material which can provide a low impedanceelectrical connection. Further, contact 36 can be of any dimension,however, contact 36 preferable has an outer diameter of 0.127 cm (0.050inches), an inner diameter of 0.102 cm (0.040 inches), and an innerdiameter of the counter-boar 640 of 0.122 cm (0.048 inches). Thepreferred dimensions of coupling 112 are discussed further below.

With reference to FIGS. 12 & 19 conductor coupling 500 of coupling 112is placed over conductor 34. Conductor 34 preferably enters a first end642 and exits a second end 644 and then is attached to conductor 34.There are many ways to attach conductor coupling 500 to conductor 34,however, it is preferred if the attachment is not by welding to preventany heat damage to conductor 34. It is further preferred if theattachment is performed by crimping to create a reliable attachment.After attachment any portion of conductor 34 extending past second end644 is preferably removed or cut away so that conductor 34 is flush withthe end of second end 644. However, it is also contemplated thatconductor 34 need not exit second end 644. Conductor 34 could extendinto conductor coupling 500 either partially or fully and still bewithin the scope of the present invention.

With reference to FIG. 20, coupling 112 is then placed into contact slot508 in direct contact with contact 36. For the following discussion,length is defined as a dimension substantially Parallel to thelongitudinal axis of contact 36. In a preferred embodiment, coupling 112has a smaller length than the length of contact slot 508. This allowsfor coupling 112 to be placed anywhere along the length of contact slot508, which makes the connection of contact coupling 502 and contact 36more accommodating for manufacturing imperfections in the conductorlength. Typically conductors are designed at very specific lengthtolerances to eliminate bending moments and tensile stresses created bybending or stretching the conductor caused by an overly long or anoverly short conductor respectively. However, due to manufacturingimperfections, conductors can be cut longer or shorter based on theconductor length tolerances. By sliding coupling 112 along the length ofcontact slot 508 any conductor length imperfections can be overcome tofurther reduce any conductor bending moments or tensile stresses. In apreferred embodiment, coupling 112 is 0.025 cm (0.010 inches) shorterthan the length of contact slot 508. However, it is contemplated thatcoupling 112 can be any length up to and including longer than contactslot 508.

With reference to FIG. 21, a front profile view shows theinterconnection between coupling 112 and contact 36. As is shown,contact slot 508 narrows from the outer diameter of contact 36 to theinside diameter of contact 36. As is also shown, contact coupling 502narrows from the outer edge of contact coupling 502 to conductorcoupling 500. In a preferred embodiment, contact coupling 502 narrowsfrom a dimension of 0.038 cm (0.015 inches) on the outer diameter ofcontact coupling 502 to 0.025 cm (0.010 inches) at conductor coupling500. The angled design of both contact slot 508 and contact coupling 502allows for coupling 112 to rest within contact slot 508 without fallingthrough contact slot 508 or without having to be held in place duringthe attachment of coupling 112 to contact 36. It is this connection,which allows for conductor 34 to be substantially coplanar with contact36. This coplanar connection eliminates any unnecessary bending momentswhich can reduce the reliability and useful life of conductor 34.Further, conductor 34 remains entirely within the implantable leadreducing any concerns with conductor-patient contact.

With reference to FIGS. 21 & 22, coupling 112 is shown after conductor34 has been attached. In this embodiment, coupling 112 has been crimpedto conductor 34. Crimp 646 is preferably made at the bottom of conductorcoupling 500 to ensure no deformities in the sides of conductor coupling500, which can result from crimping. Crimping conductor coupling 500from the bottom prevents the sides from becoming distended and thuscoupling 112 would be unable to rest substantially isodiametricallywithin contact slot 508 as shown in FIG. 21. However, it is contemplatedthat conductor coupling 500 could be crimped from the sides, but thepreferred method is crimping from the bottom of conductor coupling 500.Other methods of attaching conductor coupling 500 to conductor 34 arecontemplated such as adhering conductor coupling 500 to conductor 34with a conductive glue or providing an inner catch within conductorcoupling 500 that allows conductor 34 to enter conductor coupling butprevents withdrawal of the conductor.

With respect to FIG. 23, an implantable lead is shown with contacts 36attached thereto. As is shown, once coupling 112 is placed withincontact slot 508 and is in a position to prevent conductor bendingmoments or stress from stretching, then outside surface of contactcoupling 502 is welded to the outside surface of contact 36 asrepresented by contact weld 504. The weld 504 is performed such that theweld 504 pool is typically contained within the contact 36 perimeter. Inaddition, the weld 504 height is controlled to be less than about 0.0127cm (0.003 inch), so interaction with other devices is facilitated. Eachcontact 36 has a contact slot 508 opening that in some embodiment is inthe range from about 0.0127 cm (0.005 inch) to about 0.0381 cm (0.015inch) in width and at least about 0.0508 cm (0.020 inch) in length. Inother embodiments, the contact slot 508 can extend the entire length ofthe contact 36 as is discussed in more detail below.

With respect to FIG. 24, an implantable lead is shown with the endcontact removed. As shown, ridges 648 in the implantable lead mold willrest inside of counter-bore 640 on contact 36. Ridges 648 andcounter-bore 640 together prevent contact 36 from moving axially orradially along the implantable lead. Any pressure on contact 36 to movein an axial direction is prevented by ridge 648 making contact withcounter-bore 640. Further, with respect to FIG. 25 an alternativeembodiment for contact 36 is shown where counter-bore 640 is roundedfrom the outer diameter of contact 36 inward to the inner diameter ofcontact 36. In both embodiments, counter-boar 640 preferable extendslengthwise into contact 36 0.025 cm (0.010 inches). Counter-bore 640offers a manufacturing advantage in that if the interior of lead 30 isto be filled with an insulative material (e.g., epoxy), the insulativematerial that fills counter bore 640 keeps the insulative material fromleaking out at the edges of contact 36 during the filling process.

With reference again to FIG. 18, an isolation space 506 is createdbetween conductor 34 and contact 36 to prevent directly weldingconductor 34 to contact 36 as discussed above. Isolation space 506separates conductor 34 from weld 504 to substantially prevent conductor34 from contacting weld 504. Isolation space 506 is necessary sincesilver is not wanted in the weld pool because silver potentially weakensthe strength and integrity of a weld 504. In addition, it is desirableto avoid having silver contact the outside surface of the lead to avoidany direct contact with tissue. Although minimal silver contact withtissue is not considered harmful, the separation serves as an additionalprecaution. Isolation space 506 is greater than about 0.05 cm (0.02inch). This serves as a means for isolation created between conductor 34and contact 36 to prevent directly welding conductor 34 to contact 36.In some embodiments, isolation space 506 includes a fill material suchas epoxy. In this embodiment, isolation space 506 is provided by thespecific geometry of contact coupling 502 and more specifically thenon-welded material between conductor 34 and weld 504 to contact 36. Thenon-welded material is sized appropriately for the dimensions of thelead such as greater than about 0.005 cm (0.002 inches). In thisembodiment, the interface between the outer surface of contact 36 andthe outer surface of coupling 112 can be continuously welded alongselected sides of the interface or intermittently welded along theinterface.

FIG. 26 shows another embodiment for contact 36 and coupling 112. Inthis embodiment a “wisdom tooth” design is shown. Conductor coupling 500is made up of two side arms 650 and 652. When conductor coupling 500 isplaced over conductor 34, side arms 650 and 652 are crimped inward tosecurely hold conductor 34 substantially coplanar with contact 36.Further, as mentioned above conductor 34 could be retained withinconductor coupling 500 with conductive glue or any other means of secureattachment. Coupling 112 is then placed in contact slot 508 and thenattached to contact 36. Further, as is shown, contact slot 508 extendsthe entire length of contact 36. This allows more room in which to placecoupling 112 and reduces manufacturing costs.

FIG. 27 shows another embodiment for contact 36 and coupling 112. Thisembodiment presents a “snap lock” design. In this embodiment, conductorcoupling 500 has extending edges 654 and 656, which snap into place ascoupling 112 is placed within contact slot 508. This embodimenteliminates the need for welding coupling 112 to contact 36 or any othermeans of added attachment. However, these extra means of attachmentcould be utilized to ensure a reliable connection. In this embodiment,edges 654 and 656 preferably extend from conductor coupling 500sufficiently enough to allow coupling 112 to be pushed into contact slot508 with minimal effort as well as extending far enough to ensure areliable connection between coupling 112 and contact 36.

FIG. 28 shows another embodiment for contact 36 and coupling 112. Thisembodiment presents a “T” design. In this embodiment, coupling 112 is inthe shape of a capital “T” and rests in contact slot 508 upon ledges 658and 660. Coupling 112 is then held in place by welding or any otherreliable form of attachment.

FIG. 29 shows another embodiment for contact 36. This embodimentcontains aperture 700 to assist in keeping contact 36 from rotating andkeeping it concentric with other contacts 36. When contacts 36 aresubjected to an insert molding process where an insulative material isinjected between and under the contacts 36, this material fills aperture700. Then when this insulative material hardens, it locks contact 36 inposition and helps prevent contact 36 from rotating and assists inkeeping contact 36 concentric with other contacts 36 residing in thesame molded section (i.e., the proximal or distal end).

Thus, embodiments of the implantable lead with isolated contact coupling502 and method are disclosed to improve isolation between the contact 36and conductor 34. One skilled in the art will appreciate that thepresent invention can be practiced with embodiments other than thosedisclosed. The disclosed embodiments are presented for purposes ofillustration and not limitation, and the present invention is limitedonly by the claims that follow

1. An implantable lead with an isolated contact connection, comprising:a lead body having a proximal and distal end; at least one conductorwithin the lead body traversing from the proximal end to the distal end;at least one contact carried on the proximal end and electricallyconnected to the conductor; at least one contact carried on the distalend and electrically connected to the conductor and having an insidesurface and an outside surface and having a contact slot extending fromthe inside surface to the outside surface, the contact slot having afirst and a second edge parallel to the conductor and a proximal ordistal end which is open with no edge; and, at least one conductorcoupling being partially placed over the conductor and being attached tothe conductor; the conductor coupling being placed in the contact sloton the at least one contact, and the conductor coupling having a weld toconnect the conductor coupling to the distal end contact, wherein theconductor coupling creates an isolation space between the conductor andthe contact to prevent directly welding the conductor to the contact. 2.The implantable lead as in claim 1, wherein the isolation spaceseparates the conductor from the weld to substantially prevent theconductor from contacting the weld.
 3. The implantable lead as in claim1, wherein the isolation space is configured to reduce communicationbetween patient tissue and the conductor.
 4. The implantable lead as inclaim 1, wherein the isolation space reduces conductor ion migrationoutside of the lead body.
 5. The implantable lead as in claim 4, whereinthe conductor is braided strand wire with a silver core.
 6. Theimplantable lead as in claim 1, wherein the conductor coupling isattached to the conductor by crimping.
 7. The implantable lead as inclaim 1, wherein the weld is performed substantially on at least onecontact exterior surface for ease of manufacturing.
 8. The implantablelead as in claim 1, wherein the at least one proximal contact comprisesMP35N.
 9. The implantable lead as in claim 8, wherein the at least onedistal contact comprises a platinum-iridium alloy.
 10. The implantablelead as in claim 1, wherein the contact slot extends from a proximal endto a distal end of the contact.
 11. The implantable lead as in claim 6,wherein the conductor coupling comprises two side arms crimped inward tohold the conductor.
 12. An implantable lead with an isolated connection,comprising: a lead body having a proximal end and a distal end; at leastone conductor within the lead body traversing from the proximal end tothe distal end; at least one electrode positioned along the length ofthe lead body and electrically connected to the conductor, the electrodecomprising a hollow cylindrical tube with a first opening and a secondopening and a slot extending from the first or second opening along theelectrode substantially parallel with the lead body; and, a conductorcoupling means for attaching the electrode to the conductor, wherein theconductor coupling creates an isolation space between the conductor andan exterior surface of the electrode.
 13. The implantable lead as inclaim 12, wherein the electrode comprises a platinum-iridium alloy. 14.The implantable lead as in claim 12, wherein the conductor couplingcomprises a crimp sleeve having an aperture for receiving the conductor,the crimp sleeve being crimped to securely attach the conductor.
 15. Theimplantable lead as in claim 14, wherein the slot receives the conductorcoupling and the conductor coupling is securely attached to theelectrode.
 16. The implantable lead as in claim 15, wherein theconductor coupling is securely attached to the electrode by welding. 17.The implantable lead as in claim 16, wherein the crimp sleeve apertureis located a sufficient distance away from the weld to substantiallyprevent the conductor from being damaged by the weld.
 18. Theimplantable lead as in claim 14, wherein the crimp sleeve aperture islocated within the lead body to substantially reduce conductor ionmigration outside of the lead body.
 19. The implantable lead as in claim18, wherein the conductor is braided strand wire with a silver core. 20.The implantable lead as in claim 14, wherein the slot extendssubstantially parallel with the lead body from the first opening to thesecond opening.
 21. The implantable lead as in claim 14, wherein theconductor coupling comprises two side arms crimped inward to hold theconductor.